Enhanced transmission characteristics of on-chip interconnects with orthogonal gridded shield

Abstract

On-chip interconnects over an orthogonal grid of grounded shielding lines on the silicon substrate are characterized by full-wave electromagnetic simulation. The analysis is based on a unit cell of the periodic shielded interconnect structure. It is demonstrated that the shielding structure may help to significantly enhance the transmission characteristics of on-chip interconnects particularly in analog and mixed-signal integrated circuits with bulk substrate resistivity on the order of 10 -cm.Simulation results for the extracted transmission line parameters show a significant decrease in the frequency-dependence of the distributed shunt capacitance as well as decrease in shunt conductance with the shielding structure present, while the series inductance and series resistance parameters are nearly unaffected. An extension of the equivalent circuit model for the shunt admittance of unshielded on-chip interconnects to include the effects of shielding is also presented. Index Terms-On-chip interconnects, orthogonal gridded shield, periodic structures, shielded MIS microstrip, slow-wave transmission lines.Vijai K. Tripathi (M'68-SM'

Dispersion and resonance of on-chip interconnect lines with underlayer orthogonal metal grids

“…However, the dispersion improvement does not depend on this 0-7803-8128-9/03/$17.00 0 2003 IEEEratio. The microstrip structure, which has CO?=', shows frequency dependence, instead of dispersionless as predicted in[4]. Microstrip dispersions have been discussed intensively in[9,10], and are probably caused by mode conversions.…”

“…Aluminum is used for both metal 1 (MI) and metal 2 (M2) layers. MI line widths were kept at -2 pm, which is narrower than the grid lines discussed in [4] but more likely to be encountered in on-chip interconnect designs. Comparison structures with an MI ground plate (line #I) and without an MI layer (line #6) are also fabricated.…”

“…Experiments [3] showed reduced interconnect losses by the use of patterned ground shields [3]. Simulations [4] showed reduced frequency dependence of interconnect capacitance and conductance when orthogonal gridded shields were used 141.…”

Accurate electromagnetic full-wave modeling for interconnects in semiconductor integrated circuits

“…This minimal-loss phenomenon is similar to the ones in [44], [63], where the minimum attenuation is related to the critical substrate conductivity instead. [88], cross dots: empirical formula [56]).…”

“…Frequency behavior of (a) series resistance and (b) inductance per unit line for the MIMS structure inFig. 6.7 (circle dots: results from[88]). …”